You're right, the 30 CCC rule in wireways can be a pain, and a standard conduit body (like an LB) isn't ideal for connecting panels directly at a corner. Here's a breakdown of possible solutions, focusing on elegance, code compliance, and practicality

1. Back-to-Back Nipple Connection:
Description

This is a common approach, although sometimes tricky to execute perfectly. You use a nipple through the adjoining panel walls.

Components

Rigid Metal Conduit (RMC), Intermediate Metal Conduit (IMC), or EMT nipple (depending on your application and local codes). RMC is generally preferred for its durability and grounding capabilities. Locknuts (both inside and outside of each panel) Bushings (both inside and outside of each panel) to protect conductors.

Procedure

1. Accurately drill matching holes in both panels at the desired location.
2. Insert the nipple through both holes. Tighten locknuts on both sides of both panels. Make sure to properly ground each panel to the conduit.

Pros

Relatively simple and inexpensive. Maintains NEC separation and protection. Keeps the connection relatively tight and avoids excessive exposed wiring.

Cons

Requires very precise hole alignment. Slight misalignments can make tightening difficult and stress the conduit/panels. Can be difficult to work with in tight spaces. Requires careful installation to ensure proper grounding.

2. Short Flexible Metal Conduit (FMC) or Liquidtight Flexible Metal Conduit (LFMC) Run



Description

Use a short length of flexible conduit between the panels.

Components

FMC or LFMC (LFMC preferred for wet locations) Connectors (straight or 90-degree) listed for the conduit type. Grounding bushing (if required - see below)

Procedure

1. Attach connectors to the panels and to the flexible conduit.
2. Make a smooth, sweeping bend in the flex conduit.3. Connect the conduit.

Pros

More forgiving of slight panel misalignments. Easier to install in tight spaces. Provides vibration isolation if one panel is subject to movement.

Cons

Less aesthetically pleasing than a nipple connection (though it can still be neat). Requires careful selection of fittings for the application.

Grounding

Critical! If using FMC, a separate equipment grounding conductor (EGC) must be run inside the flex, unless the FMC meets the requirements of NEC 250.118(5)(d), which is rare (generally only requires that the FMC and associated fittings be listed for grounding.) LFMC generally requires a separate EGC because it is not inherently a good grounding conductor. Use a grounding bushing at each end to bond the EGC to the panel.

3. Milbank "Panel Mate" or Similar Adapters (as you mentioned)



Description

Specialty fittings designed for connecting enclosures. May be similar to conduit bodies but specifically designed for panel-to-panel connections.

Components

Varies depending on the specific fitting. Typically involves flanges, bushings, and connection hardware.

Procedure

Follow the manufacturer's instructions. These typically bolt onto the panels.

Pros

Designed specifically for the purpose. Often provide a clean, professional look. May include integrated grounding features.

Cons

More expensive than standard conduit fittings. May have limited availability. You have to make sure the adapter is UL Listed.

4. Using a J-Box (Junction Box) or Pull Box



Description

Instead of directly connecting the panels, you route the conductors from each panel into a J-box mounted at the corner.

Components

J-Box (metal or non-metallic, as appropriate) sized according to NEC 314.16. Conduit (EMT, RMC, PVC, etc.) from each panel to the J-box. Connectors for the conduit. Wire connectors (wire nuts, split bolts, etc.) to splice the conductors.

Procedure

1. Mount the J-box at the corner.
2. Run conduit from each panel to the J-box.3. Pull conductors from each panel into the J-box.
4. Splice the conductors together. Ensure proper grounding.

Pros

Provides a clear separation and easy access for future modifications. Can be easier to work with if there are a lot of conductors. Can be useful for adding additional circuits in the future.

Cons

More space-consuming than direct connections. More labor-intensive. Requires proper sizing of the J-box to meet fill requirements of NEC 314.16.

5. "Gutting" One Panel to Become a Junction Box



Description

Remove all the internal components of one panel and treat it as a large junction box. Run all circuits into and out of that panel.

Components

The same as using a standard J-box.

Procedure

Remove all breakers, back planes, and wiring. Use appropriately sized connectors to bring circuits into and out of the panel. Ground the panel.

Pros

May offer a cleaner look if the panel is mounted in a visible space.

Cons

Less versatile than using a true junction box. May not be practical if the panel's original purpose is still needed.

Key Considerations and Code Issues



Grounding

Absolutely critical. Ensure a reliable grounding path throughout the entire system. Use appropriately sized grounding conductors and grounding bushings/lugs as needed. Pay close attention to the grounding requirements for flexible conduit.

Fill

Make sure you are not exceeding the conduit fill limits specified in the NEC (Chapter 9, Table 1 and notes).

Conductor Type

Use conductors rated for the temperature and environment.

Support

Ensure that all conduit runs are properly supported according to the NEC.

Accessibility

Maintain required clearances around the panels. The connection method should not obstruct access to circuit breakers or other components.

Local Codes

Always consult with your local electrical inspector for specific requirements and interpretations.

Cleanliness

Neat and organized wiring is essential for safety and maintainability.

Recommendation

My preference, balancing elegance, cost, and ease of installation, is generally either:1.

Carefully executed Nipple Connection (using RMC)

For a clean, direct connection if precise alignment is possible.2.

Short Flexible Conduit (FMC/LFMC) Run: For greater flexibility and forgiveness, especially if vibration or slight misalignment is possible. Always* ensure proper grounding with a separate EGC if required.The Milbank adapters are worth investigating if you want a very polished look, but be prepared for higher costs. The J-box approach is best if you need to add flexibility for future changes.Before committing to any method, carefully measure the available space, consider the number of conductors, and plan your grounding strategy. Consult with your local electrical inspector to ensure your installation will meet code. Flag for review